Hydrogen sulfide removal from biogas and sulfur production by autotrophic denitrification in a gas-lift bioreactor

Abstract

Biogas biodesulfurization has been successfully performed in biotrickling filters (BTFs). Nevertheless, elemental sulfur (S0 ) generation and accumulation in the packed bed causes an increase in operating costs restricting its application. This drawback could be avoided using a gas-lift bioreactor as proposed in the present work, which allows recovery and re-use of the generated S0 . The effect of the governing operational parameters (nitrite concentration, nitrogen/sulfur (N/S) molar ratio, hydraulic residence time (HRT), pH, inlet load (IL) and gas residence time (GRT)) was studied. Results showed that no inhibition by nitrite was found at concentrations up to 760 mg N-NO2– L–1. H2S removal efficiencies (REs) over 95% were obtained under ILs over 55 gS-H2S m–3 h–1 when N/S molar ratios of 1.1 mol mol–1 or above were used. A HRT of 36h and pH of 7.8 ± 0.05 were found to be optimal. The maximum S0 production (99%) was obtained under an IL of 180 gS-H2S m–3 h–1 using an N/S molar ratio of 1.1 (RE = 98.1 ± 0.5%). A maximum elimination capacity (EC) of 194.2 ± 4.2 gS-H2S m–3 h–1 (RE = 83.9%) was obtained under a GRT of 41s. Therefore, gas-lift bioreactors stand as a successful and feasible alternative to BTFs to accomplish the anoxic biodesulfurization.